Hypertension (HTN), one of the most important cardiovascular risk factors, affects more than 78 million Americans. Compared to other races/ethnicities, African Americans are more likely to develop HTN and have lower rates of blood pressure (BP) control, increasing risk of premature cardiovascular morbidity and mortality. African Americans are also more likely to utilize the emergency department (ED) for ambulatory care, a factor strongly linked with adverse cardiovascular events among patients with HTN. This high ED utilization may reflect poor access to primary care, and suggests the challenge people face regarding self-management. Because BP is routinely measured in the ED, it is an ideal setting to both identify patients with uncontrolled HTN and intercede, particularly in African American communities where regular interaction with the health care system may be lacking. Recommendations to improve HTN-related outcomes have been consistent for decades: maintain a healthy weight, reduce daily sodium intake, increase physical activity, and comply with antihypertensive therapy as prescribed. Despite tremendous evidence supporting these recommendations, facilitating the necessary behavior changes in patients with HTN remains a challenge, especially in African Americans who reside in urban, under-resourced settings. Daily intensive self-monitoring is efficacious and is often the cornerstone of many behavior change interventions; however, long-term sustainment can be difficult to achieve, especially in minority populations residing in urban, under-resourced communities. Mobile health (mHealth) has demonstrated success with behavior change, and may increase long-term self- monitoring. Given high cell phone adoption rates in minority communities, and higher rates of reliance on mobile Internet access, mHealth strategies are particularly well suited to urban African American populations. Currently, there exists traction among physicians and patients for mHealth HTN interventions, but such an approach to improve BP in hypertensive patients has not been tested. This study seeks to improve HTN-related outcomes in a cohort of African Americans with uncontrolled HTN between the ages of 25 and 55, and is guided by three specific aims. Aim 1: We will determine the efficacy of MI-BP, a comprehensive, multiple health behavior change mobile intervention, on BP control at one year in a randomized controlled trial (RCT) of the intervention compared to paper-based self- monitoring and usual care controls. Aim 2: We will determine the effect of MI-BP on secondary outcomes (physical activity, sodium intake, medication adherence) compared to paper-based self- monitoring and usual care controls, in a one year RCT. Aim 3: We will evaluate the cost-effectiveness of MI-BP compared to paper-based self-monitoring and usual care controls.